JP3369693B2 - Distance measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus used for a camera or the like and for measuring a distance to a subject at the time of photographing. 2. Description of the Related Art Conventionally, as a technique for shortening a distance measuring time in a distance measuring apparatus, for example, Japanese Patent Application Laid-Open No. 1-287411 discloses the following distance measuring apparatus. This means that the light source emits light, the light reflected from the object is received by the light receiving element, and when it is determined that the object is at a short distance based on the total amount of received light, the number of light emission N of the light source is reduced,
This is to shorten the distance measurement time. Further, Japanese Patent Application Laid-Open No. 4-368906 discloses the following camera distance detecting device.
The light emitting element emits light once to measure the distance, and when the distance is short, the result is the final result. In the case of a medium distance, the distance is measured by increasing the number of times of light emission. This allows
This is to shorten the distance measurement time at a short distance. As a technique for improving the distance measuring accuracy and shortening the distance measuring time in a distance measuring apparatus, for example, Japanese Patent Application Laid-Open No. 4-307507 discloses a multipoint distance measuring apparatus as follows. . In the first ranging mode in which the ranging accuracy is low but the ranging time is short, the subject distance is roughly measured, and when the subject distance exists between the first distance and the second distance, re-ranging is performed. Do. This improves the distance measurement accuracy when the subject exists between the first distance and the second distance,
When the distance is other than that, the distance measurement is ended in the first distance measurement mode. [0005] The invention is to solve the problem
According to Japanese Patent Application Publication No. 2001-139, a light source is caused to emit light, and reflected light from a subject is received by a light receiving element, and it is determined whether the distance to the subject is short or long based on the total amount of received light. That is, if the total amount of received light is large, it is determined that the distance is short, and if it is small, it is determined that the distance is long. However, in general, the amount of reflected light from the subject is
Since it depends on the reflectance of the subject, the total amount of light received by the light receiving element changes depending on the subject. For this reason, there is a problem that a subject having a low reflectance cannot be distinguished from a subject at a long distance, and accurate distance measurement cannot be performed. Further, Japanese Patent Application Laid-Open No. 4-368906 has a problem that the light emission is performed only once at a short distance, resulting in poor distance measurement accuracy at a short distance. Also,
Japanese Patent Application Laid-Open No. 4-307507 also has a problem that the distance measurement is ended in the first distance measurement mode in which the distance measurement accuracy is low when the distance is short, so that the distance measurement accuracy in the short distance is not good. I have. Although any of the above methods can reduce the distance measurement time, it has a problem that the distance measurement accuracy is not good. Accordingly, an object of the present invention is to provide a distance measuring device having high distance measuring accuracy and a short distance measuring time. [0008] In order to achieve the above object, a distance measuring apparatus according to the present invention comprises: a light projecting means for projecting a light beam toward a distance measuring object; receiving a reflected light of the light beam from, and output light receiving means for outputting the two photoelectric conversion signal corresponding to the light receiving position, by said light receiving means
Based on the ratio of the two photoelectric conversion signals, up to the distance measurement target
Ratio calculating means for calculating the distance of
Based on the sum of the two output photoelectric conversion signals
The light amount calculating means for calculating the distance and the light emitting means
The first predetermined number of times of light emission is repeated,
Based on the output of the light receiving means at the time of repeated light emission
A first control for calculating the distance by the ratio calculating means;
Control means, and the relative performance performed by the first control means.
If the calculation result by the calculation means is shorter than the predetermined distance,
The light emitting hand is provided at a second predetermined number of times greater than the first predetermined number of times.
Light emission by the steps is repeated, and the light emission is repeated for the second predetermined number of times.
The relative performance is based on the output of the light receiving
Calculation means for calculating the distance, the first control means
The result of the calculation by the above-described ratio calculating means performed by the step is as follows.
Less than the second predetermined number of times when the distance is longer than the fixed distance
The light emission by the light emitting means is repeated
Based on the output of the light receiving means at the time of repeated light emission
A second calculation for calculating the distance by the light amount calculation means;
And control means . In the present invention, a light beam is projected by the light projecting means toward the object to be measured, and reflected light of the light beam from the object to be measured is received by the light receiving means. 2 according to position
Two photoelectric conversion signals are output. Based on the two photoelectric conversion signals, the distance to the object to be measured is calculated by the ratio calculating means or the light amount calculating means. The first predetermined number of light projections is repeated by the light emitting means, and at the time of the repeated light emission, the first control means executes a distance calculation operation by the ratio calculating means . The ratio calculating means executed by the first control means
When the result of the distance calculation operation is shorter than the predetermined distance
Is a second predetermined number of times greater than the first predetermined number of times.
The light is repeated by the light emitting means, and the light is repeatedly emitted.
Sometimes, the distance calculation operation by the ratio calculation means is performed by the second control means.
The operation is performed. On the other hand, it is executed by the first control means.
The result of the distance calculation operation by the ratio calculation means is a predetermined distance.
If it is farther than the second predetermined number of times
The light is emitted a number of times by the light emitting means,
At the time of returning light projection, by the second control means, by the light amount calculation means
A distance calculation operation is performed. [0013] [Example] In the following, the premise of the present invention with reference to the accompanying drawings tricks
A reference example of the operation and an example of the present invention will be described. First, the ranging of the subject distance will be described. FIG. 12 is a diagram for explaining the principle of triangulation used in the distance measuring apparatus of the present invention. The signal light projected from the light projecting means 11 toward the subject 13 is reflected by the subject 13. The reflected signal light is received by a position detecting light receiving element (hereinafter simply referred to as PSD) 12. Here, PSD
Reference numeral 12 is used as an example of the present invention, and is not limited to this. At this time, the object distance L can be obtained by L = B × f / Δx by detecting the shift amount Δx of the light receiving position caused by the parallax of the light transmitting / receiving means. The distance measuring apparatus of the present invention is an active distance measuring apparatus utilizing the principle of triangular distance measurement (hereinafter, referred to as ratio calculation). FIG. 1 is a functional block diagram showing the configuration of a distance measuring apparatus according to the present invention. First, a light emitting unit 1 that emits a signal light
Is connected to a CPU 2 via a driver 2 for driving the light projecting unit 1.
3 is connected. The light receiving unit 4 that receives the signal light is connected to the CPU 3 via a signal processing circuit 5 that processes a signal from the light receiving unit 4. The photographing optical system 6 is connected to the CPU 3 via a lens driving section 7. Next, the operation of the distance measuring apparatus configured as described above will be described. First, CPU
3 instructs the driver 2 to emit signal light, and simultaneously instructs the signal processing circuit 5 to prepare for signal processing. With this command, the driver 2 drives the light projecting unit 1 and the signal processing circuit 5 enters a standby state while receiving a signal from the light receiving unit 4.
After a predetermined time has elapsed in the standby state, the CPU 3 instructs the signal processing circuit 5 to start signal processing, and the signal processing is executed. The reason for providing the standby state for a predetermined time is to wait until the signal is stabilized, and the details will be described later. Next, based on the result of the signal processing by the signal processing circuit 5, the CPU 3 calculates distance measurement information.
The calculation of the driving amount of the lens included in the imaging optical system 6 is also performed. Then, the CPU 3 instructs the lens driving unit 7 to drive the lens, and adjusts the focus of the photographing optical system 6. FIG.
FIG. 3 is a diagram showing the signal processing circuit 5 and its peripheral portion in detail. First, the signal current I obtained from the PSD 12
The process of S1 will be described. The signal current IS1 output from the PSD 12 is amplified by the preamplifier Amp1 and turned back by the current mirror including the transistors Tr3 and Tr4. This is converted into a compressed voltage by the diode D1. Similarly, the signal current IS2 obtained from the PSD 12 is amplified by the preamplifier Amp2, and is turned back by the current mirror including Tr5 and Tr6. This is converted into a compressed voltage by the diode D2. The processing circuit 5 'processes these two compressed signals,
Differential and decompression arithmetic processing is performed, and based on the result, the CPU
3 performs distance measurement calculation. However, at this time, not only the signal currents IS1 and IS2 are obtained from the PSD 12 , but also the photocurrents IB1 and IB2 due to the background light.
The circuit for removing the photocurrents IB1 and IB2 due to the background light is composed of the operational amplifiers OP1 and OP2 and the transistor Tr.
1, Tr2, capacitors C1, C2 and switch SW1,
This is a circuit composed of SW2. The operation of this circuit is as follows. When the light is not projected by the light projection unit 1 shown in FIG. 1, the operational amplifiers OP1 and OP2 are activated by the CPU 3 via the switches SW1 and SW2. The operational amplifiers OP1 and OP2 perform negative feedback to control the voltages of the capacitors C1 and C2 so that the photocurrents IB1 and IB2 due to the background light all flow through the transistors Tr1 and Tr2, respectively. As described above, the photocurrents IB1 and IB2 due to the background light are removed. On the other hand, when the CPU 3 orders light emission and the light emitting section 1 emits light, the operational amplifier OP
1 and OP2 are brought into a non-active state by the switches SW1 and SW2. During the light projection, the base currents of the transistors Tr1 and Tr2 are supplied by the charges of the capacitors C1 and C2, and the photocurrents IB1 and IB2 due to the background light are removed. In this way, IS1 and IS2 are obtained, and the ratio of IS1 to IS2, or IS1 / (IS1 + IS2) or IS2 / (IS1 + IS2), causes the CPU 3 to shift the light receiving position Δx caused by the parallax of the light transmitting and receiving unit.
Is calculated. Hereinafter, the distance measuring sequence will be described with reference to a flowchart to clarify that the distance measuring time is reduced. FIG. 3 is a diagram illustrating an example of the distance measuring points A, B, and C. Here, the ranging point A indicates a subject at a short distance, and the ranging points B and C indicate subjects at a long distance. FIG. 4 relates to the technology on which the present invention is based.
9 is a flowchart illustrating a distance measurement sequence according to a first reference example . In addition, the first to fourth reference examples described below.
It is assumed that the configuration of the example and the first and second embodiments has the configuration shown in FIG. 1 and a description thereof is omitted. In steps S1, S2 and S3, the object A as shown in FIG.
The point, point B, and point C are projected eight times to measure the distance, and the respective distances La, Lb, and Lc are obtained in the ratio calculation mode. A rough distance to each subject can be obtained based on the distances La, Lb, and Lc. In step S4, a main subject is selected. Here, it is assumed that point A is selected. There are various known methods for this selection. For example, the closest subject is selected (selection 1). Further, the subject closest to the predetermined distance is selected (selection 2). If the subject at the center of the screen is shorter than a predetermined distance, the subject at the center of the screen is selected. Otherwise, the subject is selected by the method of selection 1 or 2 (selection 3). Here, the detailed description thereof is omitted. In step S5, it is determined whether or not point A has been selected. If point A has been selected, the process proceeds to step S7, and if point A has not been selected, the process proceeds to step S6. In step S6, it is determined whether or not point B has been selected. If point B has been selected, the process proceeds to step S8, and if point B has not been selected, the process proceeds to step S9. That is, when point A is selected, the process proceeds to step S7,
If a point has been selected, the process proceeds to step S8. If a point C has been selected, the process proceeds to step S9. In step S7, it is determined whether or not the distance La is shorter than a predetermined distance Ln. If the distance La is shorter, the process proceeds to step S10, and if not, the process proceeds to step S11. In step S10, actual distance measurement is performed with the number of times of light projection set to 32, and a subject distance L is obtained by ratio calculation. In step S11, the main distance measurement is performed with the number of light projections set to 64, and the subject distance L is obtained by ratio calculation. After executing steps S10 and S11, the process proceeds to step S16, and the amount of extension of the photographing lens is determined based on the results of the actual distance measurement. FIG. 5 is a timing chart showing an example of the light projection timing in each of the reference examples and the embodiments . As shown in the figure, the light emission time is 68 μsec and the light-off time is 400 μsec in one light projection. Conventionally,
Even when the distance is shorter than the predetermined value Ln or when the distance is far, the light is uniformly emitted 64 times. Therefore, under this condition, the light emission time when the main subject is closer than the predetermined value Ln is equal to the light emission time when the main subject is far. Computing how much it is shortened compared to (68 + 400) × 64− (68 + 400) × 32 = 1
4976 μsec, which reduces the distance measurement time by about 15 msec. When point B is selected, steps S8, S12, S16 or S8, S13, S
At 16, the same processing is performed. If point C is selected, steps S9, S14, S16, or S9, S15, S
At 16, the same processing is performed. FIG. 6 is a premise of the present invention.
9 is a flowchart showing a distance measurement sequence according to a second reference example of the present technology . Until the main subject is selected in steps S20 to S24, steps S1 to S1 in the first reference example are performed.
5, and the description is omitted. Thereafter, when point A is selected, step S
The process proceeds to step S26, and if the point B is selected, the process proceeds to step S28. If the point C is selected, the process proceeds to step S30. At step S26, it is determined whether or not the distance La is shorter than a predetermined value Ln1, and if it is, at step S32, the number of projections is set to 16 and actual distance measurement is performed, and the subject distance L is obtained by ratio calculation. Next, if La is longer than the predetermined value Ln1, it is determined in step S27 whether or not the distance La is shorter than the predetermined value Ln2.
The main distance measurement is performed twice, and the subject distance L is calculated by the ratio calculation.
Get. If La is far from the predetermined value Ln2, step S
In step 34, the actual distance measurement is performed with the number of times of light projection set to 64, and the subject distance L is obtained by ratio calculation. Step S32 or S33 or S
After running 34 proceeds to step S41, on the basis of the results of each of the distance measurement, determines the movement amount of the photographic lens. In the second reference example , the number of times of light emission at the time of actual distance measurement is set to three, and the number of times of light emission at a short distance is further reduced. Conventionally, the light is uniformly emitted 64 times even when the light is nearer than the predetermined value Ln1 or Ln2, and therefore, under this condition, the light emission time when the main subject is closer than the predetermined value Ln1 is longer. Calculating how much is shortened compared to the light projection time of (68 + 400) × 64− (68 + 400) × 16 = 22,264 μsec, the distance measurement time is reduced by about 2,5 msec. When the point B is selected, steps S28, S35, S41 or S28, S2
9, S36, S41, or S28, S29, S37,
Similar processing is performed in S41. If you select point C,
Steps S30, S38, S41 or S30, S3
1, S39, S41, or S30, S31, S40,
Similar processing is performed in S41. FIG. 7 is a diagram showing a third technique of the premise of the present invention.
It is a flowchart which shows the ranging sequence of a reference example .
This third reference example is different from the first reference example in that the distance L
When the distances a, Lb, and Lc are longer than the predetermined distance Ln, the distance measurement in steps S11, S13, and S15 uses the light amount calculation instead of the ratio calculation. The other steps are the same as those of the first reference example, and a description thereof will be omitted. Hereinafter, steps S51, S52, and S53 corresponding to steps S11, S13, and S15 will be described. The light quantity calculation is described in, for example, Japanese Patent Application Laid-Open No. 57-49.
As disclosed in Japanese Unexamined Patent Publication No. 905, the total light receiving amount of the PSD is calculated by adding IS1 and IS2 as described in the description of the principle of triangular distance measurement shown in FIG. Is the way. It is known that, at the time of measuring a long distance, a distance measurement result with higher accuracy than the ratio calculation can be obtained. In steps S7, S8 and S9, the distances La and L
If b and Lc are farther than the predetermined value Ln, in steps S51, S52 and S53, the number of projections is set to 64 times, the actual distance measurement is performed, and the subject distance L1 is obtained by calculating the amount of light.
Based on the result, the extension amount of the photographing lens is determined in step S16. Thereby, the distance measurement accuracy at a long distance can be improved. In the third reference example , whether or not to perform the light amount calculation is determined based on the result of the first ranging mode (steps S1 to S3). It may be determined whether or not to perform the light amount calculation based on the result of the distance mode. FIG. 8 is a diagram showing a fourth technique of the premise of the present invention.
It is a flowchart which shows the ranging sequence of a reference example . The fourth reference example is different from the second reference example in that the distances La, Lb, and Lc are longer than the predetermined distance Ln2, respectively, in the actual distance measurement in steps S34, S37, and S40. , A light quantity calculation is used in place of the ratio calculation.
The other steps are the same as in the second reference example, and the description thereof is omitted. The steps S34 and S3 are described below.
Steps S61, S62 and S63 corresponding to steps S7 and S40
Will be described. In steps S27, S29 and S31, the distance L
When a, Lb, and Lc are each farther than the predetermined value Ln2,
In steps S61, S62 and S63, the number of projections is set to 64 times, the actual distance measurement is performed, and the subject distance L1 is obtained by calculating the amount of light. Based on the result, the extension amount of the photographing lens is determined in step S41. Thereby, the distance measurement accuracy at a long distance can be improved. FIG. 9 is a flowchart showing a distance measuring sequence according to the first embodiment of the present invention. In this first embodiment,
In the third reference example , at the time of a long distance, that is, the distance La,
When the distances Lb and Lc are longer than the predetermined distance Ln, the number of times of light emission in the main distance measurement is changed from 64 times to 16 times (steps S71, S72, S73), and is reduced to less than the short distance. L1 is obtained. Generally, when the main subject is at a long distance,
It is rarely at a distance such as 0 m, and is usually at infinity or at a distance such as ten and several meters. FIG. 10 shows a calculation method for converting the distance measurement value into a reciprocal of the distance (1 / distance). As shown in the figure, it is known that approximation can be performed in a stepwise manner since there is no effect on photographing resolution even if the distance is converted stepwise at a long distance because the distance is approximated by a straight line at a medium distance and a short distance. Therefore, at a long distance, even if the error of the distance measurement value is somewhat large, the influence on the shooting resolution is small. Further, by performing the light quantity calculation, it is possible to reduce the number of times of light projection at a long distance. As described above, it is possible to shorten the distance measurement time at a long distance. The shortened distance measurement time is about 22.5 msec even at a long distance, as in the second embodiment . FIG.
FIG. 1 is a flowchart showing a distance measuring sequence according to a second embodiment of the present invention. The second embodiment is similar to the first embodiment, except that the fourth embodiment has a long distance, that is, a distance L.
When each of a, Lb, and Lc is longer than the predetermined distance Ln2, the number of times of light emission in the main distance measurement is changed from 64 to 16 (steps S81, S82, and S83) to be smaller than that in the middle distance to calculate the light amount. Thus, the object distance L1 is obtained by the following. Here, the operation, effects, and the like are the same as those of the first embodiment, and the description thereof will be omitted. The number of times of light emission, light emission time, light-off time, distance, and the like in each of the above-described embodiments are merely examples, and are not limited to those described above. Further, in each of the above embodiments, the flowchart of the three-point distance measurement is used. However, this is only an example, and it is needless to say that one point or another plurality of distance measurement may be used. As described above, according to the present invention, distance measurement can be performed in a short time without reducing the distance measurement accuracy. Therefore, it is possible to provide a ranging device having high ranging accuracy and a short ranging time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram showing a configuration of a distance measuring device according to the present invention. FIG. 2 is a diagram showing in detail a signal processing circuit 5 and its peripheral portion in FIG. 1; FIG. 3 is a diagram illustrating an example of distance measurement points A, B, and C; FIG. 4 is a flowchart showing a distance measuring sequence according to a first reference example of the technology on which the present invention is based ; FIG. 5 is a timing chart illustrating an example of light projection timing in a reference example and an example. FIG. 6 is a flowchart illustrating a distance measurement sequence according to a second reference example of the technology on which the present invention is based ; FIG. 7 is a flowchart showing a distance measuring sequence according to a third reference example of the technology on which the present invention is based ; FIG. 8 is a flowchart showing a distance measurement sequence according to a fourth reference example of the technology on which the present invention is based ; FIG. 9 is a flowchart showing a distance measuring sequence according to the first embodiment of the present invention. FIG. 10 shows a calculation method for converting a distance measurement value to 1 / distance. FIG. 11 is a flowchart showing a distance measuring sequence according to the second embodiment of the present invention. FIG. 12 is a diagram for explaining the principle of triangulation used in the distance measuring apparatus of the present invention. [Description of Signs] 1 ... light emitting unit, 2 ... driver, 3 ... CPU, 4 ... light receiving unit
Reference numeral 5: signal processing circuit, 6: photographing optical system, 7: lens drive unit, 11: light projecting means, 12: position detecting light receiving element (PS
D), 13 ... subject.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-158705 (JP, A) JP-A-4-368906 (JP, A) JP-A-4-152313 (JP, A) JP-A-1- 291111 (JP, A) JP-A-1-287411 (JP, A) JP-A-1-244310 (JP, A) JP-A-4-62412 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 3/00-3/32 G01B 11/00-11/30 102 G02B ⁷ /28-7/40 G03B 13/32-13/36

Claims (1)

(57) [Claims] 1. A light projecting means for projecting a light beam toward an object to be measured, and receiving reflected light of the light beam from the object to be measured. Light receiving means for outputting two corresponding photoelectric conversion signals, and two photoelectric conversion signals output by the light receiving means .
Comparing the distance to the object to be measured based on the ratio
Calculating means and two photoelectric conversion signals output by the light receiving means.
A light amount calculating means for calculating the distance based on the added value; and a first predetermined number of light projections by the light projection means.
The light reception at the time of repeatedly projecting light for the first predetermined number of times.
Of the distance by the ratio calculating means based on the output of the means.
A first control means for performing a calculation, and the ratio calculation means performed by the first control means.
When the calculation result is shorter than the predetermined distance, the first predetermined
The light is projected by the light emitting means at a second predetermined number of times greater than the number
The light is repeated, and the light is repeatedly projected at the second predetermined number of times.
The ratio calculating means based on the output of the light receiving means at the time.
The distance is calculated by the first control means.
The result of the operation performed by the above-mentioned ratio operation means is more than a predetermined distance.
If the distance is too far, the number of times is smaller than the second predetermined number of times.
Repeat the light emission by the light emitting means, and repeat this number of times.
Based on the output of the light receiving means at the time of returning light projection,
Second control means for calculating the distance by the calculating means
And a distance measuring device comprising: